Method of manufacturing hollow rayon fibers



May 21, 1929. W. 0.5N 1 1,713,679

METHOD OF MANUFACTURING HOLLOW RAYON FIB ERS Filed May 21, 1927 INVENTOR Mam Q and reel 7 being sufiicient to permit of the. substantially complete drying of the nitrocellulose film. The coated fiber'is removed at intervals from reel 7 and is treated with water to dissolve out the interior preliminary fiber, after which the hollow fiber is dried and is then ready for use, or may be further treated by known methods for the purpose of denitrating the nitrocellulose to reduce the flammability of the fiber.

In Figure 6 a closely related process is shown diagrammatically, 1 being the spinneret an'd,2 being the fiber drawn from the spinneret. 3 and 4 are coating wheels, coating wheel- 4 contacting with a coating fluid 6 held in tank 5, while coating wheel 3 serves the joint function of a pulley to modify the direction of the fiber, and as a secondary coating wheel obtaining coating agent by a contact with primary coating wheel 4. 7

- is a pulley for modifying the direction of motion of the fiber 2 while 8 and 9 are coating wheels, 10 is a tank and 11 is fluid in this tank. The fluid may be a coating liquid similar to that in tank 6, or it may be a coating agent of different nature, where a composite fiber is desired. "12 is a control pulley, 13 and 14 are coating wheels, 15 is a tank containing water 16, and 17 is a reel for winding the finished fiber.

Although in the diagrammatic sketches I have shown the formation of a preliminary fiber of sugar, and a coatinglayer'of nitrocellulose, it will be evident that the principle of my invention is broadly applicable to"the use of many materials as the preliminary fiber, and to many coating materials in the preparation of the final hollow fiber. As reliminary fibers I have successfully used sugar, rosin, sulfur, casein, glue and many other materials, and still other materialsmay be used, and as coating materials,

cellulose nitrate, cellulose acetate, cellulose Kant-hate, cupra-ammonium solutions of cellulose and many other like materials may be used. In all cases it is essential that the preliminary fiber should be of a soluble material, and that the solvent used in dissolving this material should not dissolve the coated material. For preliminary fibers of sugar I use water as my solvent, for preliminary fibers of rosin 'or resins I use alcohol as my solvent, and in all cases I select a solvent for my preliminary fiber which is without dissolving or other harmful action on my coating material. When coating a preliminary fiber with cellulose xanthate or with cupra-ammonia solutions of cellulose, I ma pass my fiber through a bath of any suita le coagulating or hardening material, either before or after the dissolving out of one or more stages in the process of making a composite fiber, through a mist of spray ofa coating agent or a treating agent, the excess agent being collected and reused, and in a similar way I may coagulate or harden the coating on my prepared fiber at any stage in its manufacture by the use of a gaseous or vaporous reagent, instead of using a coagulating bath ofliquid material.

My present invention is limited to the contacting of a preliminary fiber with a film of material on the surface of a suitable support in at least one operation of the process' of making a hollow fiber, the broad process of making hollow fibers by the described process, but without the use of a support carrying only a surface film of a treating agent, beingdescribed and claimed in said co-pending application S. N. 29,309. I have discovered that the use of a surface film only of a coating agent or of a modifying reagent gives fibers of somewhat more uniform nature than can be obtained by the complete immersion of the fiber in the coating agent or modifying reagent as described in said application S. N. 29,309, and the purpose of the present application is to describe and claim this modification of my earlier process. With certain coating materials there is a tendency for the liquid to form a series of small globules upon the fiber when the preliminary fiber is contacted wit-ha large excess of the coating agent, while this tendency can be controlled by bringing the fiber to be treated into contact with a thin film of the coating agent under conditions which prevent any excess'of the coating agent becoating surface of these wheels being of any desired material, and preferably of a material readily wetted by the liquid coating agent, as under these conditionsthe obtaining of a uniform thin film is automatically adjusted. Stationary Wipers or movable wiper wheels of controlled tension may of course'be employed to control the thickness of the film of treating agent held by the support, and in general the methods well known in the art may be a plied in conjunction with the specific metliod of' forming hollow fibers herein described. When coating wheels are used to apply a coating material or a treating reagent to a preliminary fiber, the fiber may wrap around the coating wheel if desired or may contact with the wheel over any desired portion of its periphery, according to the degree of contact desired.

As many modifications may be made in the described process without departing from the essential principles of the disclosure as herein made, no limitations should be placed upon my invention except such as are indicated in the appended claims.

I claim:

1. In the preparation of hollow fibers the process which comprises forming a preliminary fiber, contacting this fiber with a thin film of coating agent carried on a suitable support, transforming the liquid coating on t e fiber to solid condition and, dissolving the preliminary fiber.

2. In the preparation of hollow fibers the roccss which comprises. forming a preiminary fiber, contacting this fiber with a thin film of coating agent carried by a coating wheel, transforming the liquid coating on the fiber to solid condition and dissolving the preliminary fiber.

3. As a step in the preparation of hollow fibers the process which comprises contacting a fiber with a thin film of a liquid carried on a suitable support.

4. As a step in the preparation ofhollow fibers the process which comprises contacting a fiber with a thin film of a liquid carried on a rotatable support.

In testimony whereof, I have hereunto subscribed my name this 17th day of May,

WALTER O. SNELLING. 

